1. Technical Field
The present invention relates to a denoising method and apparatus for multi-contrast MRI's, more particularly to a denoising method and apparatus that can reduce the feel of artificiality while providing clear boundaries in the MRI's.
2. Description of the Related Art
A magnetic resonance image (MRI) is obtained by having a human body enter an apparatus that is equipped with a large magnet for generating a magnetic field, generating high-frequency waves to cause resonation in the hydrogen nuclei present in a body part, measuring the different signals released from the various tissues, and using a computer to reconstruct an image.
That is, when the apparatus equipped with a magnet emits high-frequency waves to the human body, the body may emanate echo signals, which are received, converted into digital information, and reconstructed into an image.
Unlike simple X-ray photography or CT scans, which are the medical methods that use X-ray radiation, magnetic resonance imaging is a medical imaging method that uses high-frequency waves, which are a form of non-ionizing radiation, and is thus essentially harmless to the human body. Using a magnetic field and radio frequency waves (i.e. non-ionizing radiation), which are harmless to the human body, magnetic resonance imaging can provide better contrast in internal soft tissues even without a contrast agent, compared to a CT scan, and can provide information related to the biochemical properties of tissues containing hydrogen nuclei.
Magnetic resonance imaging is similar to the CT scan in that it provides a cross-section of the human body, but whereas a CT scan focuses mainly on horizontal cross-section images, showing a horizontal cross section of the human body, magnetic resonance imaging can freely obtain images along horizontal directions, vertical directions, diagonal directions, etc., as desired, without requiring the patient to change positions.
Since a magnetic resonance image would be used by a doctor to diagnose the conditions of a patient, it is critical that noise be eliminated for improved image analysis and quantitative analysis.
A conventional method of removing noise in an image is low pass filtering (LPF). Low pass filtering employs a filter that uses average values of surrounding pixels, and while it can be effective in cases where there are no correlations between adjacent pixels, it may result in blurring and may lower the resolution of an image.
To improve this, other filters have been developed, such as the median filter, the anisotropic diffusion filter, etc. Although these filters do improve performance in noise removal, the application of such non-linear filters may cause an image to look unnatural, and detailed features may be erased.
These methods of denoising may not be suitable for magnetic resonance imaging, which especially requires detailed image analysis for accurate diagnosis.